How to reset oracle system password in 11G
Go to Start -> Programs -> Oracle –> Instance Name -> Application Development -> SQL Plus
2) In the login prompt, in the user-name field enter / as sysdba (including the forward slash) and Click OK.
3) Now you will be logged in as system with full DBA rights.
4) To reset the system password run the following query:
#alter user system identified by NewPassword;5) Replace the NewPassword with your password and enter.